Inductance coil



Aug. 18, 1925.

. A. ONWOOD INDUCTANCE COIL Filed Feb. 19,- 1923 Famed Aug. 18, 1925.

UNITED STATES res-am PATENT ,oFFicE.

ANDRE ONWOOD, OF LONDON, ENGLAND.

INDUCTANGE COIL.

Application filed February 19, 1923. Serial No. 620,095.

This invention relates to inductance coils and more particularly toinductance coils suitable for use in instruments for wirelesssignalling. An object of the present invention is to enable inductancecoils to be produced. at a cheap rate with increased mechanical strengthand, at the same time, with reduced high frequency resistance and selfcapacity. Another object of this invention is the provision of a set ofsuch inducttance coils, the coils of the set having substantially thesame winding volume and being readily interchangeable in use in the sameradio (or wireless) instrument and progressively increasing in number ofturns (and consequently in inductance) so as to permit different rangesof wave-lengths to be dealt with by the same instrument.

With these objects in view, according to the present invention, a set ofinductance coils are constructed, each without any magnetic core andeach designed for one range of a series of ranges of wave-lengths foruse, for example, in a wireless receiving instrument and constructed sothat the spacing between successive turns of a layer and the spacingbetween successive layers are different for each coil of the set. Thespacing is, in fact, less the higher the wave lengths are over which theparticular coil is designed to be employed. This results in lowerself-capacity and greater efficiency. By this means the set of coils maybe designed such that the windings for all the coilsof the set are ofsubstantially the same volume so that the coils are interchangeable foruse in the same radio receiving instrument, the coils being capable ofbeing readily substituted therein for'one another-and affording a widerange of tuning with a single instrument.

Such coils are wound on formers, the

cheeks of which are connected together wholly by means of insulatingmaterial. The members which space the cheeks apart and hold, themtogether may also serve to space apart successive layers of the winding.A convenient form of such a spacing member is a rectangular strip with areduced portion or neck near each end. The heads of said strips arepushed through narrow radial slots in the cheeks of a width suiticientto allow the smaller dimension of the rectangle to pass; then the stripis turned through a right angle so that the neck portion of the stripremains in the radial slots and holds the cheeks firmly together.

Two inductance coils constructed in accordance with the presentinvention'are illustrated' in the accompanying drawings in which MFigure 1 is a front view of a coil partly in section and with part ofone cheek broken away;

Figure 2 is an edge elevation with part of the external wrappingremoved; Y

Figure 3 is a detailed view in perspective of a spacing piece; and

Figure 4 is similar to Figure 1 and shows a modified coil, theinductance of which differs from that of the coil illustrated in Figs. 1and 2 and which may be made to serve as one of a set of inductance coilsof which the coil shown in Figs. 1 and 2' may formanother.

As shown in the drawings, each inductance coil consists substantially ofa pair of cheeks a, b which may, for example, be

stamped from vulcanized fibre. The cheeks are substantially circularwith an extension 0 at one part of the circumference. Each of thecheeks, as shown, has stamped in it nine radial slots but, of course,this number of slots may be varied. The radial slots extend down to acentre piece d consisting of a tubular piece of insulating materialserving to hold together the cheeks during winding. A. layer of wirewith the turns suitably spaced is wound upon the centre piece (I andthen one by one spacers suchas e are placed in position.

The spacer e is a rectangular strip also of vulcanized fibre with a headf, g at each end separated from the main part of the strip 6 by narrownecks h, is. The radial slots are wide enough to allow the strips 6 tobe passed through them when the latter are turned so that their largerdimension lies along the'slot. When the head portions 7', g are passedthrough corresponding slots in the two checks (1, b the strip e isturned commodate the neck portions 7t, 70 and thestrip 6 therefore holdsthe cheeks firmly spaced apart and also holds them together,

preventing them from spreading.

When a complete ring of such spacers is placed in position, the windinggoes on to form a second layer around these spacers; then a second ringof spacers is placed in position and another layer wound. The winding isclearly seen at Z in Figures 1 and 4:. This method of winding goes onuntil the inductance of the coil has reached the desired value, the twoends of the winding being connected to terminals and the coil completedby a covering of waterproof tape m.

The terminals in the "form illustrated com prise a pair of split pinsn,'0 which are screwed into a block p of insulating material. The blockg) has a width equal to the distance between the cheeks and is of a sizeto fill in the spaces between the two extensions dot the cheeks. It isheld in position there by screws 0". The split pins are screwed throughthe block p until shoulders s abut against the outer surface of theblock p. The ends of the coil are soldered to the inside ends of thepins n, 0, the inner end of the wire being brought up outside the cheekat around spacing strips as seen clearly at t. It is worthy f note thatapart from the conductor Z of the coil, the only metal parts used arethe terminal ins a, 0' and the screws 1". These are place apart from thewinding and thus produce practically no losses in the coil." Ofcourse,-it is quite easy to take any number of tappings fromintermediate points in the winding and then, of course, more than twoterminals will be necessary. It will be noted that when the coil iscomplete, all the spacing pieces engaging with the side cheeks a, I)give great rigidity which ensures constant values for the electricalconstants of the coil. It is convenient from the manufacturing point ofview, for all the spacers to be of one size. They may be, for example,of a cross-section one-eighth of an inch by one-sixteenth of an inch andthen whenmore than one-sixteenth of an inch is desired betweensuccessive layers, two or more spacers can be used together. The onlydifference, in this respect, between the coils shown in Figures 1 and 4is that in Figure 1, as can be seen, there are two spacers between,successive layers of the coil and in Figure 4 there are three, spacersbetween successive layers.

In making a set of inductance coils of this pattern for a wirelessreceiver, for example, it is clear that the inductance coils for thelower ranges of wave length will have a ma am comparatively few turnsand both the turns and successive layers will be spaced well apart; thusa number of spacing pieces 6 will be used between successive layers. Forthe higher ranges of wave length, however, with a greater number ofturns in each coil, less spacers will be used between successive coilsand b this arrangement a set of coils esigned sothat the total volumecan be so of the winding. is substantially the same for all the coils(as will be observed upon comparing the windings shown in Figs. 1 and 4).This, of course, has the advantage of standsults the still furtheradvantage that the several coils of the set are interchangeable for oneanother in use in a radio receiving set (or instrument) that is, in theeveiitthat the set of coils is used in conjunction with a Wirelessreceiving instrument wherein the tuning is effected by one or morevariable condensers, and it be desired to listen in to signals on acomparatively low wavelength, there is selected from the set of coilsone of the coils that is formed with a relatively small number of turnsand the pins 11, 0, of this selected coil are inserted in the socketsprovided in the Wireless receiving set, this pin-and-socket connectionbeing the only switching connection required. Tuning is now sought t beeffected by means of the condenser. If itshould appear that the signalsare being transmitted on a wavelength that is higher than any includedwithin the range of the chosen coil, the chosen coil is removed from theradio instrument and is replaced therein by an appropriate coil from thesame set of coils, the substituted coil having, of course, a largernumber of turns to permit tuning for the higher wave-length on which thesignal is apparently being sent. This replacement manoeuvre orsubstitution of one coil for another of the same set of coils in thesame radio instrument makes the apparatus capable of receiving signalsover a wide range of wave-lengths and is practicable to be effected forthe reason that the coils, although varying widely in number of turnsand so in inductance, are formed on mountings that "are entirely similarin shape and dimensions and are so wound that their winding-volumes aresubstantially identical or the same, as herein shown and described.Moreover, the winding-volumes being the same, the air-spaces between therelatively few turns of the coils designed for use where the signals arebeing transmitted on a comparafrequency currents.

tivelylow wave-length, are wide, and this results in the reduction ofthe self-capacity of such coils to almost the vanishing point and in theavoidance of an increase of the natural wave-lengths of such coils dueto coils designed for use with relatively high wave-lengths and it ispracticable to place the turns of fine wire quite close together sothatthe air-spaces therebetween are relatively narrow and thewindingwolumes of these coils may be made the same as thewinding-volumes of the coils of few turns of coarse wire.

If desired, of course, a space may be left through the windings, so thata rod could be passed completely through the winding along a diameterand would then serve to rotate the coil.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is 1. An inductance coil comprising a pair ofcheeks of insulating material formed with However, the objec tions basedon the ground of self-capacity are by no means so important in the caseof a plurality ofradial slots, a pluralityof insulating strips engagingsaid slots to space said cheeks apart and to hold them together,

and a winding wound in spaced layers, each layer being wound over a ringof said insulating straps.

2. A former for an inductance coil comprising a pair of cheeks formedwith a plurality of radial slots and a plurality of 40 headed spacingstrips adapted to protrude through corresponding radial slots of saidtwo cheeks and engage the latter to maintain them in spacedrelationship.

l 3. A former for an lnductance co1l,com-

prising a pair of cheeks of insulating mate rial formed with apluralityof radial slots and a plurality of headed spacing strips ofrectangular sections and of dimensions enabling the strips to be passedthrough the 5 slots and to be turned to lock the said cheeks in spacedrelationship.

4.- A11 inductance coil comprising a pair of cheeks of insulatingmaterial formed with a plurality of radial slots, a winding wound inspaced layers and a plurality of rings of insulating spacing stripsintroduced between each pair of adjacent layers to engage correspondingslots in said cheeks to maintain said cheeks in spaced relationship.

ANDRE o-Nwoon.

